1. Field of the Invention
Embodiments of the present invention relate generally to optical communication systems and components and, more particularly, to a packaged stack of optical devices.
2. Description of the Related Art
In a wavelength division multiplexing (WDM) optical communication system, information is carried by multiple channels, each channel corresponding to a unique wavelength. WDM allows transmission of data from different sources over the same fiber optic link simultaneously, since each data source is assigned a dedicated channel. The result is an optical communication link with an aggregate bandwidth that increases with the number of wavelengths, or channels, incorporated into the WDM signal. In this way, WDM technology maximizes the use of an available fiber optic infrastructure; what would normally require multiple optic links or fibers instead requires only one.
In WDM optical communication systems, it is often necessary to add, drop, and/or attenuate a light beam. This can be achieved by an optical switching device, which directs an input light beam to one of multiple output optical paths. For example, in a 1×2 optical switching device, an input light beam enters through an input fiber and is directed to one of two output fibers. There are also more complicated optical switching devices, such as 2×2, 1×N, and N by N switching devices, which are sometimes realized by combining several 1×2 devices. In some optical networks, the individual wavelength channels of a WDM input signal are directed to different output fibers by an optical switching device, such as a wavelength selective switch (WSS) or an optical add-drop multiplexer (OADM). In addition, individual wavelength channels of a WDM input signal may be attenuated by an optical switching device, such as a dynamic gain equalizer (DGE).
The optical switching devices for WDM communication systems, such as WSSs, OADMs, and DGEs, are quite complex, and include active and passive optical elements that must be manufactured and aligned to high tolerances for proper operation of such switching devices. Because of this, the manufacturing costs for assembly, testing and quality assurance of WDM optical switching devices are substantial. As bandwidth requirements for optical communication networks increase, it is desirable to reduce per-channel manufacturing costs and improve per-channel mean time between failure (MTBF) of WDM optical switching devices.
Accordingly, there is a need for optical switching devices used in communications networks, e.g., WSSs, OADMs, and DGEs, for which the per-channel cost is reduced and MTBF is improved without adversely affecting network bandwidth.